In flat panel display technology, organic light emitting diode (OLED) displays have many advantages such as light and thin, active illumination, fast response, wide viewing angles, wide color gamut, high brightness, and low power consumption. OLED displays have gradually become the third-generation display technology after liquid crystal displays. Compared with liquid crystal displays (LCDs), OLED have advantages of more power savings, thinner, and wider viewing angles, which is unmatched by LCDs. At present, people are increasingly demanding higher level of detail, that is, the resolution, but production of high-quality, high-resolution OLED displays still faces many challenges.
With development of display technology, OLED panels are being adopted by more and more electronic products, and flexible OLEDs have attracted much attention due to their flexibility. Touch sensor used in flexible OLED panel is mainly out-cell type, that is, the sensor module is completed on the film layer structure and then attached to the OLED panel. The production of touch sensor directly on flexible OLED panel needs to consider influence of the electron emission layer (i.e., the cathode) of OLED on the touch sensor signal.
In existing technology, touch sensor is divided into two types: self-capacitance and mutual capacitance:
1. The mutual capacitance touch screen has a large capacitance between the electron emission layer (i.e., the cathode) of OLED and touch sensor, resulting in a large capacitance, which affects the sensitivity of the touch.
2. The self-capacitance touch screen (single layer multi-point) divides the entire screen into M*N areas, each area is a separate transparent conductive electrode block, and each transparent conductive electrode block passes the signal line and touch on the same layer. That is, each transparent conductive electrode block independently forms a capacitance to the surrounding environment. When finger approaches a transparent conductive electrode at a certain position, a coupling capacitor is introduced, causing the detected capacitance to increase, and the IC determines that the position is touched. However, since the signal line occupies a part of the touch screen, the touch cannot be achieved at this position. Therefore, the single-layer multi-point self-capacitance touch screen has poor touch precision issues.